1. Technical Field
The present invention concerns equipment for the removal of ingots, in particular billets, after casting, i.e. lifting the cast billets out of a casting pit after the end of the casting cycle and transferring the billet(s) to the desired transport equipment for transport on to a store or further treatment/processing.
2. Description of the Related Art
In the production of primary aluminium or remelting of aluminium, cast objects in various formats are produced, for example sheet ingots that are used when rolling aluminium into thin aluminium strips or foil and billets that are used when extruding aluminium into extended aluminium sections with different cross-sections and designs.
Both sheet ingots and billets are produced by semi-continuous casting equipment that comprises a large number of chills arranged in rows in a frame structure. Liquid metal is added to the chills via a metal manifold through a hot-top from above into the cavity of each chill. The metal is cooled and solidified in two stages. Stage 1 is called primary cooling, in which the initial solidification of the metal is achieved via cooling through the wall of the cavity in the chill. Stage 2 is called secondary cooling, in which water immediately below the primary cooling area is sprayed directly against the metal via a water gap or holes along the circumference of the chill. The equipment is placed over a casting pit with a depth equivalent to the casting length of the billets to be cast plus the structural height of a mobile support, a total depth of in the order of 10-11 meters. The mobile support under the chills is moved downwards as the metal solidifies in order to create extended bodies in the form of the billets specified, equivalent to the number of chills, which may have different diameters between 150 and 400, depending on the intended use of the billets.
After each casting operation, the casting equipment is lifted or removed in some other way from the opening over the casting pit so that the cast billets are exposed and can be removed from the casting pit. This removal is currently performed using a travelling crane with a spreader that is provided with a number of rings, each of which is connected to the spreader with a wire. Each of the rings is threaded manually down onto the end of a billet and, by lifting the spreader and thus pulling on each wire, each ring is pulled obliquely so that, by squeezing, it retains the billet onto which it is threaded and can lift the billet. In each lifting operation, a row of billets is normally lifted right out of the pit at once and then laid horizontally on a transport device, normally a roller conveyor, for transport to a store or further treatment/processing. The lifting operation in which the billets are lifted right out of the casting pit means that the fall height for the billets is high in the event of an accident. This, along with the fact that the billets are handled manually, entails a high risk for the operators who perform the work and a risk of serious injury to them.
The equipment for casting billets otherwise normally comprises several tens of chills and thus several tens of billets that need to be removed after each casting cycle. The removal work is therefore also time-consuming, which, in turn, reduces the total casting capacity.